Mold clamping device

ABSTRACT

A mold clamping device includes a base, a stationary platen fixed to the base and supporting a stationary mold, a movable platen movable on the base and supporting a movable mold, and a mold clamping mechanism for clamping the movable mold against the stationary mold. Tie bars extend from the stationary platen completely through both the movable platen and the mold clamping mechanism. A shaft supporting plate is fixed to the base and has openings through which the tie bars slidably extend for supporting the tie bars. The shaft supporting plate terminates at its lower end portion in two spaced-apart shoes that are fixed to the base. The bottom surface of each shoe has a larger area than the cross-sectional area of the shaft supporting plate situated vertically above the shoe.

FIELD OF THE INVENTION

The present disclosure relates to a mold clamping device that clampsmetal molds.

BACKGROUND

An injection molding apparatus includes, as primary components, aninjection device and a mold clamping device. The injection deviceinjects a resin material into metal molds. At this time, it is necessaryto keep closing the metal molds against injection pressure. Accordingly,the mold clamping device keeps clamping the metal molds.

An example known mold clamping device is disclosed in, for example,Japan Patent No. 2675425.

The technology disclosed in Japan Patent No. 2675425 will be describedwith reference to FIG. 8.

As illustrated in FIG. 8, a mold clamping device 100 includes a base101, a stationary platen 102 fixed to the base 101, a movable platen 103placed on the base 101 so as to correspond to the stationary platen 102,a mold clamping cylinder 104 that pushes out the movable platen 103toward the stationary platen 102, tie bars 105 which are extended fromthe stationary platen 102 and which pass completely through the movableplaten 103 and through the mold clamping cylinder 104, and a shaftsupporting plate 106 which is fixed to the base 101 and which supportsthe tips of the respective tie bars 105. The stationary platen 102supports a stationary mold 107. The movable platen 103 supports amovable mold 108. The mold clamping cylinder 104 includes half nuts 109.A fast-forward cylinder 111 is connected to the movable platen 103 andto the shaft supporting plate 106.

The half nut 109 is disengaged (unlocked). A piston rod 104 a of themold clamping cylinder 104 is caused to be freely movable in the axialdirection. In addition, the movable platen 103 is fast-forwarded towardthe stationary platen 102 by the fast-forward cylinder 111. In thiscase, the movable mold 108 abuts the stationary mold 107.

Next, the half nut 109 is engaged with the corresponding tie bar 105.After the engagement, the mold clamping cylinder 104 is fixed to the tiebar 105. Subsequently, the piston rod 104 a of the mold clampingcylinder 104 is moved forward. Consequently, the movable mold 108 issubjected to mold clamping with the stationary mold 107 by intensiveforce.

At the time of this mold clamping, the tie bars 105 are slightlyelongated between the stationary platen 102 and the half nut 109. Thatis, when a distance between the stationary platen 102 and the half nut109 is L1, this L1 changes to L1+α (where α is an elongated amount andis a positive value).

In contrast, the tie bar 105 is slightly compressed between the half nut109 and the shaft supporting plate 106. That is, when a distance betweenthe half nut 109 and the shaft supporting plate 106 is L2, this L2changes to L2−α.

When the tie bar 105 is elongated, although the outer diameter thereofdecreases, the linearity is maintained.

In contrast, when the tie bar 105 is compressed, it is curved like aline A, and thus the linearity is no longer maintained. When the tie bar105 is curved, the shaft supporting plate 106 is curved like a line B.

The shaft supporting plate 106 has a primary role to support the tip ofthe tie bar 105. The shaft supporting plate 106 is also a basal pointfor the fast-forward cylinder 111. Hence, curving of the shaftsupporting plate 106 is not preferable.

In order to address this technical problem, the shaft supporting plate106 may be thickened (in a horizontal direction in the figure) toenhance the rigidity of the shaft supporting plate 106.

When the thickness increases, the weight of the shaft supporting plate106 increases, resulting in an increase in weight of the mold clampingdevice 100.

In view of a request for weight saving of the mold clamping device, itis not preferable to increase the thickness of the shaft supportingplate.

SUMMARY OF THE INVENTION

An objective of the present disclosure is to provide a mold clampingdevice capable of avoiding an increase in weight while preventing a tiebar from being bent.

According to a first embodiment of the present disclosure, a moldclamping device includes:

-   -   a base;    -   a stationary platen fixed to the base and supporting a        stationary mold;    -   a movable platen supporting a movable mold that corresponds to        the stationary mold;    -   a mold clamping mechanism that clamps the movable mold against        the stationary mold;    -   a tie bar extended from the stationary platen and passing        completely through the movable platen and through the mold        clamping mechanism; and    -   a half nut mechanically connecting the mold clamping mechanism        to the tie bar.

The mold clamping device further includes a shaft supporting platesupporting a tip of the tie bar, and

-   -   the shaft supporting plate is fixed to the tip of the tie bar,        and is mounted on the base so as to be freely movable.

According to the present disclosure, the shaft supporting plate is fixedto the tip of the tie bar, and is mounted on the base so as to be freelymovable. When compression force is applied between the shaft supportingplate and the molding clamping mechanism, the shaft supporting platemoves on the base. This movement addresses the compression force.Consequently, the tie bar is not curved. Since the tie bar is notcurved, the shaft supporting plate is not curved. Since not curved, therigidity of the shaft supporting plate can be reduced, enablingthinning, and weight saving.

According to the present disclosure, the mold clamping device capable ofavoiding an increase in weight while preventing a tie bar from beingbent. is provided.

According to a second embodiment of the present disclosure, a moldclamping device includes:

-   -   a base;    -   a stationary platen fixed to the base and supporting a        stationary mold;    -   a movable platen supporting a movable mold that corresponds to        the stationary mold;    -   a mold clamping mechanism that clamps the movable mold against        the stationary mold;    -   a tie bar extended from the stationary platen and passing        completely through the movable platen and through the mold        clamping mechanism; and    -   a half nut mechanically connecting the mold clamping mechanism        to the tie bar.

The mold clamping device further includes a shaft supporting platesupporting a tip of the tie bar.

The shaft supporting plate is fixed to the base and is provided with athrough-hole through which the tip of the tie bar passes.

The tie bar is supported by the shaft supporting plate so as to befreely movable.

According to the present disclosure, the shaft supporting plate is fixedto the base, and is provided with the through-hole through which the tipof the tie bar passes. The tie bar is fitted in the through-hole so asto be freely movable. When compression force is applied between theshaft supporting plate and the mold clamping mechanism, the tie barmoves relative to the shaft supporting plate. This movement addressesthe compression force. Consequently, the tie bar is not curved. Sincethe tie bar is not curved, the shaft supporting plate is not curved.Since not curved, the rigidity of the shaft supporting plate can bereduced, enabling thinning and weight saving.

According to the present disclosure, the mold clamping device capable ofavoiding an increase in weight while preventing a tie bar from beingbent. is provided.

Preferably, the shaft supporting plate may include:

-   -   a pair of columns extending upwardly from the base;    -   an upper cross member extending horizontally and connecting the        respective upper portions of the columns to each other; and    -   a lower cross member extending horizontally and connecting        respective middle portions of the columns in a height direction.

Since the shaft supporting plate is a rectangular frame, the shaftsupporting plate can be made further lightweight.

Preferably, a shoe that has a larger bottom area than a cross-sectionalarea of the column as viewed from a bottom may be provided at a lowerend of the column.

Since the shoe is provided at the lower end of the column, the shaftsupporting plate can stand upright stably.

BRIEF DESCRIPTION OF THE DRAWINGS

Several preferable embodiments of the present disclosure will bedescribed below in detail with reference to the accompanying figures inwhich:

FIG. 1 is a side view of a mold clamping device according to the presentdisclosure;

FIG. 2 is a diagram as viewed along an arrow 2 in FIG. 1;

FIG. 3 is a diagram as viewed along an arrow 3 in FIG. 1;

FIG. 4A is a diagram illustrating the mold clamping device when a halfnut is in an unlocked condition;

FIG. 4B is a diagram illustrating the mold clamping device when the halfnut is in a locked condition;

FIG. 5A, FIG. 5B, FIG. 5C, and FIG. 5D are diagrams for describingvarious forms of a shoe;

FIG. 6 is a diagram for describing an example in which an attachedposition of a fast-forward cylinder is changed;

FIG. 7 is a side view of a mold clamping device according to a modifiedexample of the present disclosure; and

FIG. 8 is a diagram for describing a basic structure of a conventionaltechnology.

DETAILED DESCRIPTION OF THE EMBODIMENTS First Embodiment

A mold clamping device according to a first embodiment will be describedwith reference to FIG. 1 to FIG. 6.

As illustrated in FIG. 1, a mold clamping device 10 includes a base 11,a stationary platen 12, a movable platen 13, a mold clamping mechanism14, tie bars 15, and a shaft supporting plate 30.

The stationary platen 12 is fixed to the base 11.

The movable platen 13 is placed on the base 11 so as to be freelymovable.

The mold clamping mechanism 14 has a role of pushing out the movableplaten 13 toward the stationary platen 12.

The tie bars 15 are each extended from the stationary platen 12, andpass completely through the movable platen 13 and through the moldclamping mechanism 14.

The shaft supporting plate 30 is placed on the base 11, and supportstips of the respective tie bars 15.

The stationary platen 12 supports a stationary mold 17. The movableplaten 13 supports a movable mold 18.

Preferably, a rail 19 is placed and laid over on the base 11. Moreover,a first slider 21 and a second slider 22 are placed on this rail 19 soas to be freely movable. The first slider 21 supports movable platen 13,and the second slider 22 supports the mold clamping mechanism 14. Notethat there is no problem if either one or both of the movable platen 13and the mold clamping mechanism 14 are directly placed on the base 11.

Moreover, the shaft supporting plate 30 may be directly placed on thebase 11, or may be indirectly placed on the base 11 indirectly via therail or the slider.

The mold clamping mechanism 14 includes half nuts 23.

The tie bars 15 each include a toothed portion, such as a sawtoothportion 24, corresponding to each half nut 23.

Preferably, a position adjusting actuator 25 is connected to the moldclamping mechanism 14 and to the movable platen 13.

Moreover, fast-forward mechanisms 26 are connected to the movable platen13 and to the shaft supporting plate 30.

Note that although a hydraulic cylinder is suitable for the moldclamping mechanism 14, an electric motor cylinder that has a built-inball screw or a toggle mechanism may be adopted.

Furthermore, although an electric motor cylinder that has a built-inball screw is suitable for the position adjusting actuator 25, ahydraulic cylinder or a pneumatic cylinder may be adopted.

Still further, although a hydraulic cylinder is suitable for eachfast-forward mechanism 26, an electric motor cylinder that has abuilt-in ball screw may be adopted.

As illustrated in FIG. 2, the shaft supporting plate 30 includes a pairof right and left columns 31 that extends upwardly from the base 11, anupper cross member 33, and a lower cross member 34.

The upper cross member 33 is extended horizontally, and connects theupper portions of the respective columns 31.

The lower cross member 34 is extended horizontally, and connects theintermediate portions of the respective columns 31 in a heightdirection.

The shaft supporting plate 30 is provided with a rectangular opening 35between the upper cross member 33 and the lower cross member 34, and isprovided with a horizontally-long opening 36 between the lower crossmember 34 and the base 11.

In comparison with a simple wall shape, the shaft supporting plate 30can be a solid body except the rectangular opening 35 and thehorizontally-long opening 36, thus can be lightweight by whatcorresponds to such openings. However, there is no technical problem ifthe shaft supporting plate 30 is formed in a simple wall shape.

The shaft supporting plate 30 moves from the front side of FIG. 2 to thedepth side thereof. In order to guide the moving shaft supporting plate30, a side guide 42 may be provided on the base 11. However, since themoving distance is quite short, the side guide 42 may be omitted.

As illustrated in FIGS. 1-3, the shaft supporting plate 30 terminates atits lower end portion in two spaced-apart shoes 37. Each shoe 37 has aflat bottom surface in direct sliding contact with the base 11, and theflat bottom surface of each shoe has a larger area than thecross-sectional area of the shaft supporting plate 30 situatedvertically above the shoe 37. In this embodiment, each column 31 of theshaft supporting plate 30 includes, as viewed from a the bottom(underside), a shoe 37 that has a larger bottom area than across-sectional area of the column 31. That is, each column 31 includesa projecting portion 38 that projects toward the stationary platen 12illustrated in FIG. 1. In FIG. 1, when a horizontal external force isapplied to the shaft supporting plate 30, since the shaft supportingplate 30 is provided with the projecting portions 38, such a plate isnot likely to fall down.

With reference to FIG. 4A and FIG. 4B, an action of the mold clampingdevice 10 that employs the above-described structure will be described.

As illustrated in FIG. 4A, the half nuts 23 are changed to a release(unlocked) condition. This causes the mold clamping mechanism 14 and themovable platen 13 to be freely movable in the axial direction. Inaddition, the movable platen 13 is fast-forwarded toward the stationaryplaten 12 by the fast-forward mechanisms 26, and causes the movable mold18 to abut the stationary mold 17.

Next, the mold clamping mechanism 14 is moved horizontally by theposition adjusting actuator 25 with reference to the movable platen 13until the male threads of the respective half nuts 23 are meshed withthe female threads of the respective sawtooth portions 24.

When the movement is completed, as illustrated in FIG. 4B, therespective half nuts 23 are engaged with the respective sawtoothportions 24. The mold clamping mechanism 14 is mechanically coupled tothe tie bars 15, and is fixed thereto.

Next, the piston rod 14 a is moved forward by the mold clampingmechanism 14. Consequently, the movable mold 18 is subjected to moldclamping with the stationary mold 17.

At the time of this mold clamping, the tie bars 15 are slightlyelongated between the stationary platen 12 and the respective half nuts23. Simultaneously, the tie bars 15 are about to be slightly compressedbetween the respective half nuts 23 and the shaft supporting plate 30.

However, according to the present disclosure, since the shaft supportingplate 30 moves on the base 11, no compression phenomenon occurs. Sincenot compressed, the tie bars 15 are not curved, and the shaft supportingplate 30 is also not curved.

Another shape of the shoe 37 will be described with reference to FIG. 5Ato FIG. 5D.

As illustrated in FIG. 5A, the projecting portion 38 may be extended toan opposite side to the stationary platen (reference numeral 12, in FIG.1).

As illustrated in FIG. 5B, the projecting portion 38 may be extendedtoward both the stationary platen and a side opposite to the stationaryplaten.

As illustrated in FIG. 5C, the projecting portion 38 may be provided soas to surround the entire circumference of the column 31.

That is, as illustrated in FIGS. 5A to 5C, since the shoe 37 that has alarger bottom area than the cross-sectional area of the column 31 isprovided at the lower end of the column 31, the column 31 can standupright from the base stably.

Note that as illustrated in FIG. 5D, a shape that has no projectingportion 38 may be adopted.

Meanwhile, in FIG. 2, the fast-forward cylinders 26 are placed at middle(including substantially middle) positions between the upper and lowertie bars 15. Although this is a quite rare case, when the movable platen(reference numeral 13 in FIG. 1) is fast-forwarded, the movable platendoes not move smoothly.

An example structure that addresses such a problem will be describedwith reference to FIG. 6.

As illustrated in FIG. 6, one of the pair of fast-forward mechanisms(cylinders) 26 may be placed above the middle position between the upperand lower tie bars 15, and the other may be placed below the middleposition between the upper and lower tie bars 15. That is, the pair offast-forward cylinders 26 is placed at diagonal positions. The onefast-forward cylinder 26 becomes distant from the base 11, while theother fast-forward cylinder 26 becomes close to the base 11. Since boththe distances differ, the movement of the movable platen becomes smooth.

Second Embodiment

A mold clamping device according to a second embodiment will bedescribed with reference to FIG. 7. Note that the common component asthat in FIG. 1 will be denoted by the same reference numeral in FIG. 1.

The mold clamping device 10 illustrated in FIG. 7 differs from the moldclamping device 10 illustrated in FIG. 1 such that the shaft supportingplate 30 is fixed to the base 11 by bolts 39, etc., and the tie bars 15pass completely through the shaft supporting plate 30.

That is, the shaft supporting plate 30 includes through-holes 41 throughwhich the tips of the respective tie bars 15 pass completely. The tipsof the respective tie bars 15 are fitted in the respective through-holes41. The tie bars 15 are supported by the shaft supporting plate 30 so asto be freely movable.

At the time of mold clamping, the tie bars 15 are slightly elongatedbetween the stationary platen 12 and the respective half nuts 23.Simultaneously, the tie bars 15 are about to be slightly compressedbetween the half nuts 23 and the shaft supporting plate 30.

However, according to the present disclosure, since the tie bars 15 movein the shaft supporting plate 30, no compression phenomenon occurs.Since not compressed, the tie bar 15 are not curved, and the shaftsupporting plate 30 are not curved.

As described with reference to FIG. 1 and FIG. 7, according to thepresent disclosure, the shaft supporting plate 30 does not disrupt themovement of the tie bars 15 in the axial direction. Hence, no horizontalexternal force is applied to the shaft supporting plate 30. The shaftsupporting plate 30 accomplishes only a role of supporting the tips ofthe tie bars 15. Since it is adequate for the shaft supporting plate 30to merely accomplish a role of supporting a part of the weight of eachtie bar 15, a large rigidity is unnecessary. Consequently, the shaftsupporting plate 30 which has a low rigidity, thin, and lightweight canbe adopted.

The present disclosure is suitable for a mold clamping device thatincludes a shaft supporting plate.

What is claimed is:
 1. A mold clamping device comprising: a base; a stationary platen fixed to the base and supporting a stationary mold; a movable platen supporting a movable mold that corresponds to the stationary mold; a mold clamping mechanism that clamps the movable mold against the stationary mold; a tie bar extended from the stationary platen and passing completely through the movable platen and through the mold clamping mechanism; a half nut configured to mechanically connect the mold clamping mechanism to the tie bar; a shaft supporting plate fixed to the base and having a through-opening through which the tie bar slidably extends for supporting the tie bar, the shaft supporting plate terminating at its lower end portion in two spaced-apart columns, each column terminating at its lower end in a shoe, each shoe having a larger bottom area than the cross-sectional area of its respective column, and the shoes being fixed to the base; and two fast-forward mechanisms each connected to the movable platen and to the shaft supporting plate for fast-forwarding the movable platen toward the stationary platen.
 2. The mold clamping device according to claim 1, wherein the two columns extend upwardly to an upper end of the shaft supporting plate, and wherein the shaft supporting plate further includes an upper cross member extending horizontally and connecting respective upper portions of the columns to each other, and a lower cross member extending horizontally and connecting respective middle portions of the columns to each other.
 3. The mold clamping device according to claim 1, wherein each shoe includes a projecting portion that projects from a side of its respective column toward the stationary platen, the projecting portion being fixed to the base thereby fixing the shaft supporting plate to the base.
 4. The mold clamping device according to claim 3, wherein the projecting portion of each shoe projects from, and surrounds, the entire periphery of its respective column.
 5. The mold clamping device according to claim 3, wherein each shoe includes another projecting portion that projects from an opposite side of the column than the first-mentioned projecting portion.
 6. The mold clamping device according to claim 1, wherein the movable platen and the mold clamping mechanism are disposed between the stationary platen and the shaft supporting plate; and the tie bar comprises plural tie bars connected to the stationary platen and extending slidably through through-openings in the movable platen, the mold clamping mechanism and the shaft supporting plate.
 7. The mold clamping device according to claim 6, wherein the through-openings in the shaft supporting plate are provided in the columns.
 8. The mold clamping device according to claim 6, wherein the two columns extend upwardly to an upper end of the shaft supporting plate, wherein the shaft supporting plate further includes an upper cross member extending horizontally and connecting respective upper portions of the columns to each other, and a lower cross member extending horizontally and connecting respective middle portions of the columns to each other, and wherein the through-openings in the shaft supporting plate are provided at the intersection of the columns and the upper and lower cross members.
 9. The mold clamping device according to claim 6, wherein each shoe includes a projecting portion that projects from a side of its respective column toward the stationary platen, the projecting portion being fixed to the base thereby fixing the shaft supporting plate to the base.
 10. The mold clamping device according to claim 9, wherein each shoe includes another projecting portion that projects from an opposite side of the column than the first-mentioned projecting portion.
 11. The mold clamping device according to claim 9, wherein the projecting portion of each shoe projects from, and surrounds, the entire periphery of its respective column. 